Freshly made strawberries & balsamic onions on brioche sit on cutting board on April 9th, 2014 in San Francisco, Calif.

Freshly made strawberries & balsamic onions on brioche sit on cutting board on April 9th, 2014 in San Francisco, Calif.

Photo: Paige Hermreck, Special To The Chronicle

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Strawberries get early start

Strawberries get early start

Photo: Craig Lee, Special To The Chronicle

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How to choose as spring strawberries roll in early

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The first blush of spring is colored by rosy red strawberries, one of California's most prized crops. This sweet-tart taste of spring deserves a lot of love and appreciation, since harvesting the berries is labor intensive - they're picked, sorted and packed by hand in the field.

California farmers - about 400 of them - grow about 88 percent of the nation's crop, according to the California Strawberry Commission. California strawberries are available practically year-round. April through October is harvest time for the more northern strawberry producers, with peak production from April through July. The southern part of the state produces lesser amounts in December through June.

This year's season started earlier than usual because of the warm weather. The lack of rain did not affect growers who irrigated, but those who depend on surface water have concerns about summer crop production.

But late-season rain can also be problematic. When almost-ripe strawberries are picked after a heavy rain, they can get watery in flavor and texture, as happens with other fruit, such as tomatoes.

Varieties: Out of the 100-plus varieties, about 16 are commercially grown. In addition, there are about half a dozen proprietary varieties.

Charles Okui of Okui Farms in San Luis Obispo County considers the dark red, conical Albions the best-tasting berry. Okui also grows a newer variety - the Monterey - which is slightly bigger and less firm than the Albion.

Swanton Berry Farm's Jim Cochran grows Chandlers at his Davenport ranch. It's an older variety, which turns a nice, deep red when ripe. He says they are often oddly shaped and can be rather flat and wide, though as the season progresses, the berries become smaller and more regular in shape.

More prolific Seascapes, which produce 50 percent more fruit than the Chandlers, are bright red and have a more conical strawberry shape. Fraise de bois - also called the Alpine or wild strawberry - is just now commercially available from Happy Quail Farms in East Palo Alto.

Nutrition: One serving (about eight medium strawberries) contains about 45 calories and provides more vitamin C than an orange.

How to select: Contrary to belief, smaller berries do not always taste sweeter. Choose strawberries that have a good aroma, which can indicate good flavor.

When ripe, the color of strawberry varieties can vary from a more medium red to deep red, so color is not always an indicator. However, since they do not ripen after being picked, choose strawberries that are fully red without any white or green, with fresh-looking caps.

How to store: Arrange them in a single layer in a paper-towel-lined container; cover and refrigerate. Rinse them right before eating to avoid spoilage, and try to eat them within a couple of days.

Strawberries & Balsamic Onions on Brioche

Serves 4

Serve this as a starter or as a brunch side dish. Balsamic vinegar - with its acidity and touch of sweetness - is the key to bringing this dish together. The vinegar should be very subtle. If you use aged balsamic or a balsamic reduction, you'll need the smaller amount listed since they're sweeter than basic balsamic vinegars. Note that the onions can be made ahead.

3 small yellow onions, about 1 1/2 pounds

3 to 4 tablespoons olive oil

1/2 to 1 teaspoon balsamic vinegar, to taste

-- Kosher salt and black pepper, to taste

4 slices of brioche, about 1/2-inch thick (see Note)

-- Unsalted butter, softened

-- Strawberries, rinsed and hulled

-- Thinly shredded basil

Instructions: Peel and quarter the onions; slice thinly crosswise. Place in a large, dry sauté pan over medium heat. Cover and cook, stirring once, until onions are dry and start to stick to the pan, 5-10 minutes.

Add the oil, reduce heat to medium-low and continue to cook, uncovered, until onions are deep golden brown, 15-30 minutes, depending on the heat. As the onions start browning more, you will need to stir more frequently.

Remove the onions to a bowl; add balsamic vinegar, salt and pepper. Set aside to cool to room temperature. You will have about 1 cup. The onions can be done ahead and refrigerated; bring to room temperature before continuing.

Toast the brioche. Butter one side of each piece, then arrange about 1/4 cup of the onions on top. Slice the strawberries and arrange them, shingle-style, atop the onions. Garnish with basil.

Note: Trader's Joe's carries loaf brioche. You can also use challah, which is more widely available.